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Updated: Aug 14, 2025

Preparation of Contiguous Bisaziridines for Regioselective Ring-Opening Reactions
Published on: July 28, 2022
Selective 3,3-Rearrangement of Azobenzenes upon Complexation by a Frustrated Lewis Pair
Lucas Wickemeyer1, Israel Fernández2, Beate Neumann1
1Lehrstuhl für Anorganische Chemie und Strukturchemie and Centrum für Molekulare Materialen CM2, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany.
Abstract:
The reaction of the oxygen-bridged frustrated Lewis pairs (FLPs) tBu2 P-O-Si(C2 F5 )3 (1) and tBu2 P-O-AlBis2 (2) with azobenzene, promoted by UV irradiation, led to a selective complexation of the cis-isomer. The addition product of 2 is stable, while the adduct of 1 isomerizes in solution in an ortho-benzidine-like [3,3]-rearrangement by cleavage of the N-N bond, saturation of the nitrogen atoms with hydrogen atoms and formation of a new bond between two phenyl ortho-carbon atoms. Similar rearrangements take place with different para-substituted azobenzenes (R=Me, OMe, Cl) and di(2-naphthyl)diazene, while ortho-methylated azo compounds do not form adducts with 1. All adducts were characterized by multinuclear NMR spectroscopy and elemental analyses and the mechanism of the rearrangement was explored by quantum-chemical calculations.
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